1. Field of the Invention
The present invention relates to valves for controlling fluid flow in an internal combustion engine. More particularly, the present invention relates to reed valves for controlling intake and/or transfer fluid flow in such engines.
2. Background of the Prior Art
Reed valves are presently widely employed in internal combustion engines to control air or air/fuel intake. In two-stroke cycle engines, such as disclosed in U.S. Pat. Nos. 3,905,340, 3,905,341, and 4,051,820, such reed valves play an important role in supporting the improved operation of the engine and the proper transfer of air and fuel from crankcase to combustion chamber. More recently, such reed valves also have been employed in four-stroke cycle engines to control air intake and improve engine performance.
In U.S. Pat. No. 3,905,340 it is disclosed that significant improvements in reed valve life and performance may be achieved by substituting a multiple stage reed valve design in place of a conventional single stage reed. In the design disclosed in that patent, a relatively stiff primary reed is utilized having ports therein. A secondary reed member is then oriented over the ports in the primary reed, with a secondary reed petal sealing each of the primary reed ports. The secondary reed member provides fluid flow through the ports in the primary reed member. In order to allow such flow, the secondary reed members are far more flexible than the primary reed so that the secondary reed member opens farther than the primary reed during the pressure changes each engine cycle. The invention of the '340 patent improves engine performance in virtually all applications and, due to the reduced stresses inherent with this design, reed valve life is dramatically increased.
Although the multi-stage reed disclosed in U.S. Pat. No. 3,905,340 functions very well, it has been found that further improvements are possible. One problem is that many intake passages have uneven flow distribution through them which results in greater stress placed on certain petals of the secondary reed. As a result of the increased stresses placed on only some of the reed petals, the over-stressed petals will undergo material fatigue and break far more rapidly than less stressed reed petals. Applicant's U.S. Pat. No. 4,696,263 attempts to address this problem in part by providing a protective coating of synthetic rubber on the reed valves to prolong their life.
Further, uneven flow distribution through the air intake, conventional or multi-staged reeds do not provide optimum air intake distribution into the engine. One solution to this problem is addressed in applicant's U.S. Pat. No. 4,879,976 for an aeroform reed valve cage which modifies the intake passage upstream from the reed valves so to provide more even air flow through the reed valves. Another approach to solving this problem is disclosed in U.S. Pat. No. 5,036,806 which calls for joining together the reed petals of the secondary reed member to improve intake flow and reduce reed petal fatigue. A further approach to improving reed valve performance is shown in applicant's U.S. patent application Ser. No. 740,447, now allowed U.S. Pat. No. 5,176,170, which employs thicker reed valve material and wider reed ports and petals for improved life and flow characteristics.
Notwithstanding these advances, additional improvements in reed valve performance and life are shown to be possible. First, smoother, less turbulent flow is possible by controlling the flexing of the primary reed to provide a smooth uniform bend from the base of the reed to its apex. It has been determined that this can be accomplished by carefully controlling the shape of the beam or beams between adjacent ports of a multi-ported primary reed so that regardless of the pressure on the reed valve there is a uniform bend along its entire height. Also, it has been determined that by making the beams between adjacent ports as narrow as possible as they approach the apex of the primary reed, a further contribution to more smooth flow is realized. In combination with this primary reed, a secondary reed of rectangular shape with no interruptions, openings or slots, and covering all ports in the primary reed further contributes to smoother, less turbulent flow through the valve.
Of greater importance in improving reed valve performance is controlling the relative opening of the primary reed and secondary reed. The conventional approach to dual stage reed valves was to have the second stage reed open first with a low pressure differential, followed by opening of the primary reed upon increased pressure differential. However, it has been found that increased flow rates and increased power can be obtained by having both the secondary and primary reeds initiate their opening substantially simultaneously. It has further been determined that the rate of opening of the primary reed should be approximately one-half of that of the secondary reed for maximum performance. By controlling the contour of the primary reed member and movement of the secondary reed member, the desired relationship of movement of the primary and secondary reed members can be obtained. Further, the same means for controlling opening of the reed members can be utilized to control the bending of the reed members so that the reed members bend in an arcuate form of uniform radius, thereby eliminating stress concentrations, prolonging life of the reed members and providing flow conditions with minimum turbulence.
Accordingly, it is a primary object of the present invention to provide an improved reed valve which provides all the benefits of prior multi-stage reed valves while having improved flow characteristics, improved performance, and further increased operating life.
It is a further object of the present invention to provide a reed valve with the above advantages which employs a novel design and shape of the beams between ports of a multi-port primary reed for improved flow characteristics.
A further object of the present invention is to provide novel reed valve members for a multi-stage reed valve wherein the primary and secondary reed valve members initiate their opening substantially simultaneously and the primary reed valve member opens at a rate approximately one-half of that of the secondary reed valve member, providing improved flow characteristics.
It is another object of the present invention to provide a reed valve with the above advantages which better complements advancements in aerodynamic reed cage technology.
It is an additional object of the present invention to provide a reed valve with the above advantages which is straightforward in design and adds no weight, complexity, or expense to the engine or the air intake system.
These and other objects of the present invention will become evident from review of the following specification.